Background: Split cord malformation (SCM) is a rare condition. With decreasing incidence of neural tube defect (NTD) in the West, the reports of SCM are getting lesser and lesser. However, in India, spinal dysraphism is still a major problem encountered by the neurosurgeons. Objective: Our aim was to analyze 300 patients of SCM for their clinical features, radiological findings and outcome of surgery, which can throw light on the subject to others, who have less scope of finding these cases frequently. Materials and Methods: Over a 16-year period, we encountered 300 cases of SCM at AIIMS. Over the same period, more than 1500 cases of NTD were managed. SCM was noticed in 20% of cases with NTD. Skin stigmata were noted in two-third of the cases, and scoliosis and foot deformity were observed in 50% and 48% cases, respectively. Motor and sensory deficits were observed in 80% and 70% cases, respectively. Commonest site affected was lumbar or dorsolumbar (55% and 23%, respectively). In 3% cases, it was cervical in location. Magnetic resonance imaging (MRI) scan revealed a large number of anomalies like lipoma, neuroenteric cyst, thick filum and dermoid or epidermoid cysts. All the patients were surgically treated. In type I, bony spurs were excised, and in type II, bands tethering the cord were released. Associated anomalies were managed in the same sitting. Patients were followed up from 3 months to 3 years. Results: Overall improvement was noticed in 50% and stabilization in 44% cases and deterioration of neurological status was recorded in 6% cases. However, 50% of those who deteriorated improved to preop status prior to discharge, 7-10 days following surgery. Conclusions: SCM is rare and not many large series are available. We operated 300 cases and noticed a large number of associated anomalies and also multilevel and multisite splits. Improvement or stabilization was noted in 94% and deterioration in 6% cases. We recommended prophylactic surgery for our asymptomatic patients.

Overall, there is a decreasing trend in neural tube defect (NTD) in the world literature. Since 1950, the incidence has fallen from 40-50/10,000 live births to 3-4/10,000 live births. There is no report of exact incidence available from the Indian subcontinent. However, over the last 20 years in our center, the incidence of NTD has gone up, primarily for two reasons. Firstly, we have been pragmatically and scientifically looking at these problems to provide rational treatment. [1],[2],[3] Secondly, with MRI investigation of scoliosis patients and patients with only skin stigmata, the number of patients referred to us with lipoma and split cord malformation (SCM) has also increased over the years. In this study, we analyze 300 cases of SCM, which is the largest series in the world literature so far.

Materials and Methods

At AIIMS, in Department of Neurosurgery, from 1990 to 2006, over 1500 cases of spinal dysraphism were operated. Amongst them, 300 were with SCM. These patients were retrospectively studied for clinical profile, magnetic resonance imaging (MRI) findings, surgical procedures and outcome. Patients with only skin stigmata with SCM were also operated prophylactially after explaining the procedure to the parents in detail, so that future deterioration can be prevented. All the patients were followed up in the out-patients department and the follow-up period ranged from 3 months to 3 years.

Results

Clinical presentation had two peaks, 1-3 years of age and also 12-16 years of age. Skin stigmata and orthopedic deformity were noticed in 60% and 90%, respectively [Figure 1]a-d. Commonest orthopedic problem was scoliosis, followed by lower limb deformity [Table 1].

Neurological deficit was recorded in 80%. Motor, sensory or both was noticed in all; and only 25% had autonomic disturbances. Fifteen percent had trophic ulcer in the lower limbs. In 20% cases, there was no neurological deficit [Table 2].

MRI was performed in all the patients to find out the type of SCM [Figure 2]b and c, number of segments, multiple sites of NTD and other associated anomalies like lipoma, thick filum, dermoid and epidermoid tumors, neuroenteric cyst and dermal sinus. Type I SCM [Figure 2]a was noticed in 45% and type II in 55% [Table 3] patients.

Figure 2: (a) CT scan of a patient with SCM type I with posterior spur arising from lamina. (b) Axial MRI of spine showing type I SCM with two hemicords in two separate sheaths. One hemicord has syringomyelia. (c) Coronal MRI shows type I a spur at the center with large space above and below the spur

SCM was most common in lumbar area (55%) followed by dorsolumbar area in 23% [Figure 3]a-c. Only in 3%, the SCM was found in cervical region, and in 8% it was present in lumbosacral area. Long segment of SCM type I was noticed in 5% and it was found in multiple sites in 2% patients [Table 4].

All the patients were subjected to surgical exploration and excision of spur. Laminotomy was carried out in all the patients using Midas Rex high-speed drill. In all patients with type I SCM, bony spur was excised by using fine Kerrison Ronguer or by using diamond drills. In case of type I SCM, two dural tubes were converted to one dural tube. The anterior dura was left open and the posterior one was closed after excising intradural bands and median nerve roots to untether the spinal cord.

In case of type II SCM, after the laminotomy, dura was opened. All the extradural and intradural bands were excised to untether the cord. Associated lesions like dermoid, epidermoid, lipoma and neuroenteric cyst were also excised. In all patients, the filum terminale was also excised to release the traction on the conus [Figure 4]a-c.

There were six patients with posterior spurs [Figure 2]a. In these patients, laminotomy was difficult and care was taken to remove the lamina where the base of the spur was originating from the lamina. In these cases, chances of rupturing the dura and lacerating the spinal cord were higher. Hence, utmost care had to be taken to prevent the damage in posterior/dorsal spur. After the base was tackled, the removal of rest of the spur was easy. All the patients received antibiotics for 2 days postop and were discharged between 7 and 10 days following surgery.

Follow-up and outcome

Postoperatively, the patients were discharged on 7 th -10 th day and were regularly followed between 3 months and 3 years. Overall improvement occurred in 50% patients, and 44% patients remained unchanged. Immediate postop neurological deterioration was noticed in 6%. However, 50% of those who deteriorated improved to the preoperative status within 7-10 days, by the time they were discharged. Only 3% patients of the entire series had deteriorated in neurological status and showed partial recovery in long-term follow-up. None of the patients who had prophylactic surgery had neurological deterioration [Table 5].

SCM is a rare form of NTD described in the world literature. [1],[2],[3],[4],[5],[6] However, because of high incidence of NTD in India, we have dealt with a large number of patients with SCM. [2],[3],[4] In a study from Iran, amongst the 330 cases of meningomyelocele (MMC), 33 patients had SCM. [5] We have seen more than 400 cases in the last 20 years. However, this study only includes 300 cases admitted between 1991 and 2006; during the same period, we managed approximately 1500 patients of NTD.

SCM can be associated with a large number of anomalies. [5],[6],[7],[8],[9],[10],[11],[12],[13] Common associations are MMC, [5],[6] lipoma, [7],[8],[9] teratomas [10],[11],[12] and neuroenteric cyst. [13] Among the MMC, SCM is reported in 10% cases. [5] We also have encountered MMC in a large number of patients with SCM. Sometimes the MMC arises from one hemicord. [14] We have also operated a large number of patients in whom MMC was arising from one hemicord at the site of the split.

The common site of SCM is dorsolumbar area and lumbar area, as reported by us and others. [1],[2],[3],[4],[5],[15],[16] Pang, [16] in 2001, described ventral tethering in a series of 11 patients among the 52 patients with type II SCM. He described four types of ventral spurs. Rarely, spurs can be arising from dorsal side, that is, from the spinus process and the apex of the spur goes toward the posterior aspect of the vertebral body. [17],[18]

In the present study, 6 among the 300 patients with SCM had posterior spur, where the base of the spur was attached to the inner surface of laminae, tip of the spur going anteriorly after splitting the spinal cord. Rarely, SCM is reported in cervical and sacral areas. [19] Three patients in our study had cervical split and 10% had sacral or lumbosacral split. Finding of multiple sites of split is rare. We have encountered four cases of multiple site split in our study.

A large number of systemic anomalies are also reported with SCM. Renal and urogenital anomalies, CVS anomalies and anorectal anomalies are not uncommon in patients with SCM. [7],[8],[14],[20],[21] Jindal et al., [22] had reported a patient of SCM who had eventration of the diaphragm. Cases of situs inversus have also been reported. [21] Rarely, SCM is also reported in adults. [23],[24]

Skin stigmata are well recognized and reported in occult spinal dysraphism with SCM. [3],[10],[19],[20] Izci et al., [25] in 2007, highlighted the diagnostic value of skin marker. In our earlier studies, we reported hypertrichosis, nevus, dimple and dermal sinus in a large number of patients. [1],[2],[3] In the present study, 60% patients had cutaneous marker and 80% had scoliosis or lower limb deformities, which are the evidence of SCM in a large number of cases.

MRI is the investigation of choice in these patients. All our patients had spinal MRI at the suspected site of the lesion and MRI cranio vertetral junction (CVJ) to exclude Chiari malformation More Details. [1],[2],[3],[16] In fact, MRI is useful to find associated anomalies like lipoma, neuroenteric cyst or dermoid epidermoid tumor. MRI is also useful to find out thick or fatty filum. Because of the MRI screening of the whole spine, we have been able to detect multisite spinal dysraphism with multiple site SCM in four cases, which would have been missed if MRI had been performed only for the local site with skin stigmata.

There are several classifications of SCM. Pang, in 1992, classified SCM into type I and type II. Furthermore, SCM can be complex SCM. [21] The complexity is because of associated anomalies like lipoma, teratoma and dermoid epidermoid tumors. Another classification is into ventral and dorsal type I spur. [16],[17],[19] SCM could be in single site or in multiple sites.

Mahapatra and Gupta [3] and Gupta and Mahapatra [26],[27] classified type I spur into a-d types, depending on the location of spur in between the proximal part and distal part of the split, the space available above and below the spur. This classification has a direct relation to the surgical approach and risk of postoperative deterioration. Thus, the type of SCM I can determine the surgical approach.

Surgical excision is the treatment of choice. [1],[2],[3],[4],[15],[16] In our study, all the patients were operated. There are considerable controversies regarding the need for surgery in all type II patients and in SCM patients with no neurological deficit. In our study, 20% patients were asymptomatic. All asymptomatic patients were also subjected to surgery, as we consider surgery is safe with reasonably low risk. [1],[2],[3]

Surgery was well planned to treat the bony or fibrous spur and simultaneously tackle the associated pathologies like lipoma, teratoma or dermoid epidermoid tumors. In every patient, filum was also excised. When the SCM was far from the conus, it was treated, and through a separate incision at L 4 - L 5 level, the filum was exposed and excised. Excision of filum also helped in reducing the traction on the conus. [2],[3] Over the last 8-10 years, we have treated type I SCM depending on its subtype (a-d). Our surgical strategy for SCM type I has changed our outlook and also improved the result by lesser handling of the spinal cord. We routinely performed laminoplasty using high-speed drill, however, we feel in neonates and infants, laminotomy can be formed using fine Kerrison's punch.

Outcome of the patients with SCM is generally gratifying. [1],[2],[3],[15],[26],[27] All the tethering elements must be taken care of to release the spinal cord. In dorsal spurs, care must be taken not to damage the cord by performing laminotomy. In complex split cord, the associated pathology must be treated. We performed surgery to treat all elements in the same sitting to avoid repeated admission and repeated anesthesia. Pang, in 2001, reported 51 patients with type II SCM, in whom 11 had ventral tethering, which must be inspected and tethering elements must be removed. He also concluded that MRI is ineffective to diagnose the ventral tethering, for which CT myelogram is ideal and partially effective and could detect ventral tethering in 50% of the patients.

Overall outcome of SCM is good. Proctor and Scott [15] reported long-term good results. They studied neurological status, pain, bowel and bladder disturbances and spinal deformity. Two out of 16 patients in their series had retethering. In our study, all the patients did not have a long-term follow-up. However, approximately 7-10% patients develop retethering over a period of 5 years. One of the causes of the retethering is the regrowth of the spur [28] and development of postoperative arachnoiditis. Gupta et al., [28] reported regrowth of a bony spur in 2010. Thus, regrowth of the spur must be carefully evaluated and excised, in case the patient starts deteriorating in neurological status. In our study, 50% showed postoperative improvement and 44% remained unchanged. In 25% patients, bladder and bowel problem also improved. Deterioration of neurological state was recorded in 6%. None of the patients undergoing prophylactic surgery had postoperative neurological deterioration. Thus, over the last two decades, our conviction for surgery in asymptomatic cases has become strong and robust.

Conclusions

SCM is a rare condition. We have seen 300 cases in a period of 16 years (1991-2006). MRI is the investigation of choice. A large number of patients had other associated spinal pathologies, which made them complex split. Six patients had dorsal spur, which needed special care. Our classification, type I SCM a-d, is based on our clinical and radiological observations, which guides to surgical approach and good outcome. Retethering is possible in 10% and regrowth of a bony spur must be considered. We recommend prophylactic surgery, as in our experience none of the asymptomatic patients deteriorated following surgery.